Control system



Jan. 21, 1941. G. E. KING 2,229,414

CONTROL SYSTEM Filed May 25, 1958 2 Sheets-Sheet 1 WITNESSES: INVENTORGeargeE K2775. BY

2 ATTORNEY Jan. 21, 1941. G, E. KING 2,229,414

CONTROL SYSTEM Filed May 25, 1938 2 Sheets-Sheet 2 I -69 a 65 gWITNESSES: INVENTOR George E K2729.

#m; 7%. MEY-MM ATTORNEY Patented Jan. 21, 1941 UNITED STATES CONTROLSYSTEM George E. King, Wilkinsburg, Pa., assignor to WestinghouseElectric a Manufacturing Company, East Pittsburgh, Pa., a corporation oiPennsylvania Application May 25, 1938, Serial No. 209,971

14 Claims.

This invention relates to control systems and more particularly tocontrol systems for auto matically controlling the operation ofreversing motors used to drive reciprocating mechanisms,

such as planers, draw-cut shapers, roll grinders,

transfer tables, etc.

In planers and similar machine tools, a work carrying table orreciprocating member is reciprocated by a motor with respect to acutting tool. The motor is controlled by means of a stroke limit switchwhich in turn is controlled by dogs mounted on the work table. The workmay be a costly die to be machined up to a shoulder or a large casting,portions of which are too large to pass certain parts'of the machine.Failure of the limit switch to operate may result in damage to the workor to the machine, or injury to the operator.

It is, accordingly, an object of my invention to provide apparatus, in acontrol system incorporating selective means for reversing a motor, forstopping the motor in event of .a failure of the selective means.

Another object of my invention is to provide apparatus, in a controlsystem incorporating selective means for reversing a motor at apredetermined time, for stopping the motor before the predetermined timein event of a failure of the selective means.

Another object of my invention is to provide apparatus, in a controlsystem utilizing a braking eil'ect initiated by selective means, forapplying a greater braking effect for stopping a motor within apredetermined limit in event of failure of the selective means.

A more specific object of my invention is the provision of two stoppingmeans for a motor, one for stopping the motor from a given speed and agiven rotor position in a substantially predetermined number ofrevolutions, and the other, normally becoming efiective later than thefirst and after failure of the first to initiate the stopping of themotor, for stopping the motor from the same given speed in substantiallythe same numher of revolutions or a lesser number counting therevolutions from the same given rotor position.

A further object of my invention is to stop a machine element from agiven speed to standstill within a given distance of travel from a givenpoint, at which the stopping is normally initiated,

even though the stopping operation may be initiated after the machineelement has passed said given point.

It is also an object of my invention to provide,

in combination with normally used stopping means forv an electric motorto stop an electric motor from a given speed in a given time interval,apparatus for stopp the electric motor in a lesser interval of time inthe event of a failure of the normally used stopping means. 5

A broad object of my invention is to provide a more rapid rate ofretardation of a machine element from a given speed of movement tostandstill in the event a slower rate of retardation of the machineelement was not previously initi- 1 ated.

In general, it is an object of my invention to provide apparatus thatshall be simple and reliable in operation and adapted for ready andeconomical manufacture. 15

In the following discussion, the invention is treated in connection witha planer, and, more particularly, the planer platen, but the inventionis not limited in its use to the control of pianers, but may be appliedgenerally where rapid reversal of a motor-driven machine is desired.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its 25 method ofoperation, together with additional objects, and advantages thereof,will best be lmderstood from the following description of a specificembodiment when read in connection with the accompanying drawings, inwhich: 30

Figure 1 is a diagrammatic view of a system of control organized inaccordance with the present invention;

Fig. 2 is a view in front elevation of a planer operated by a controlsystem construction in 35 accordance with the present invention; and,

Fig. 3 is a view in front elevation of a stroke limit switch constructedin accordance with the present invention, and with parts broken away forclearness. 40

In Fig. 1, motor ll having an armature I3, a

series field winding l5 and a shunt field winding I1 is shown. The motorIt is utilized for driving a reciprocating member or platen I! on aplaner bed 2| of the planer in Fig. 2. A control cabinet 45 23 houseselectromagnetic devices, utilized for controlling the motor I I,including a main contactor 25, reversing switch 21 and 29, startingswitch 3|, dynamic braking switch 33, field relays 35, 31 and 33,plugging relay 4| and auxiliary 50 relays 43, 45 and 1.

A pushbutton station or pendant switch 49 from which complete control ofthe motor is bad, includes an inch cut pushbutton switch 5|, an inchreturn pushbutton switch 53, an automatic 55 cut pushbutton 55, anautomatic return push button switch 51 and the stop switch 59.

Below the planer platen I9 and at the side of the planer bed 2| ispositioned a limit switch 6| having projecting levers 63, 65 and 61. Atthe side of the platen |9 are positioned a pair of lugs or dogs 69 and1| which may be adjusted longitudinally oi the platen I9 within groovesof T-shape. The dogs and projecting levers are so disposed that the dog59 engages levers 63 and 65 and the dog 1| engages levers 61 and 65 whenthe platen is reciprocating.

If it be assumed that the planer platen I9 moves to the right (Fig. 3),or in the cut direction, dog 69 actuates projecting lever 63 whichinitiates a dynamic-braking eflect in the motor to stop the planerplaten I9 within a definite distance of travel and, for any given platenspeed, within a definite time after actuation of the projecting lever63. The dog 69 actuates the projecting lever 65 an instant after theactuation of the projecting lever 63. As the planer platen moves to theleft, or in the return direction, the dog 69 again actuates the lever65, and an instant thereafter actuates the lever 63 moving lever 63 toits original position. A similar function is performed by the dog H andthe projecting levers 61 and 65.

The limit switch 6| is shown diagrammatically in Figs. 1 and 2. Theprojecting lever 63 is mechanically connected to actuate simultaneouslya plurality of sets of contacts, including the cut directional contacts13 and the auxiliary contacts 15. Similarly, the projecting lever 61 ismechanically connected to actuate simultaneously a plurality of sets ofcontact members including the return directional contacts 11 and theauxiliary contacts 19. Various contact arrangements well known in theart may be utilized, the essential characteristic of the contacts beingthat they may be held positively in the open or in the closed position.It will be apparent that projecting levers 63 and 61 are always in agiven position, the set position, when the planer platen I9 is in aposition intermediate the limits of travel determined by the positionselected for the dogs 69 and 1|. When projecting levers 63 and 61 are inset position, the directional contacts 13 and 11 are in the circuitclosing position, while the auxiliary contacts 15 and 19 are in thecircuit opening position.

The projecting lever 65 is mechanically connected to a set of contacts8| which are biased in the circuit closing position by a pair ofdifferentially connected springs 83. The contacts 8| open when the lever65 is actuated by either dog 69, or dog 1|. It is sufiicient that thecontacts 8| remain in the circuit opening position only momentarily whenthe lever 65 is actuated by either dog 69, or dog 1|. It will readily beunderstood that various types of contact members may be utilized such assliding contacts, or quick make and break contacts.

Electrical energy is supplied to the control system from a pair ofenergized conductors or buses and 81. Upon closure of a disconnectingswitch 89, operating coils 9|, 93 and of the relays 35, 31 and 43,respectively, become energized. The circuit for operating coils 9| and95 may be traced from the energized conductor 85 through the switch 89,conductor 99, contacts IUI of reversing switch 21, contacts I03 ofreversing switch 29, conductor I05 where the circuit divides, one branchextending through the operating coil 9| to the energized conductor 81,and

another branch extending through the closed contacts 8|, the operatingcoil 95 to the energized conductor 81. It will be noted that the openauxiliary contacts 15 and 19 are connected in parallel circuit relationwith the contacts II. The circuit for operating coil 93 extends fromconductor 99, through operating coil 93, contacts I01 of starting switch3|, conductor I09, to the energized conductor 81. Energization ofoperating coil 93 actuates field relay 31 to close a set of contacts I II, thus shunting a field rheostat ||3.

Energization or operating coil 9| actuates a field relay 35 to opencontacts I I1 and to close contacts II5. A circuit is thus establishedfor the shunt field winding I1, and it extends from the energizedconductor 85, switch 89, conductor 91, contacts II5, conductor II9,contacts III, resistor I2I, field winding I1, conductor I99 to theenergized conductor 81.

Energization of the operating coil 95 actuates the auxiliary relay 43 toopen contacts I23 and close contacts I25. Thus a holding circuit isestablished for the operating coils 9| and 95, and it extends fromenergized conductor 91, contacts II5, conductor II9, contacts I25,resistor I21, conductor I05, from where the circuit continues throughoperating coils 9| and 95 as hereinabove described.

Assuming that the planer platen is between the limits of travel and theattendant wishes to start the planer platen for automatic operation inthe out direction, the pushbutton 55 is depressed, thereby establishinga circuit from the energized conductor II9, contacts I25, conductor I29,operating coils I3I and I33, directional contacts 13, upper contacts ofreturn pushbutton 51, lower contacts of cut pushbutton 55, stop switch59, operating coil I35 of auxiliary relay 45 to the energized conductor81.

Upon the energization of actuating coil I35, contact members I31, I39and I are closed and contact members I43 and I45 are opened. 010- sureof contacts I31 establishes a holding circuit for operating coil I35which extends from the energized conductor I29, contacts I31, resistorI41, stop switch 59, operating coil I35, to the energized conductor 81.

Closure of the contacts I39 establishes a circuit which extends from theenergized upper contacts of pushbutton 51, to contacts I39, contactsI49, operating coil I5| of directional contactor 21 to the energizedconductor 81. Thus the operating coils I3I, I33 and |5| become fullyenergized and actuate substantially simultaneously main contactor 25,dynamic-braking switch 33 and cut reversing switch 21, respectively.

Energization of operating coil I33 thus opens contacts I53 to open thecircuit through dynamic braking resistor I55.

Energization of operating coil I 5| opens contacts IIII and I51, andcloses contacts I59, I8! and I63. Energization of operating coil |3Iopens contacts I 65 and closes contacts I61 and I69.

Closure of contacts I61, I59 and I6I establishes circuits for energizingarmature I3 of motor II, and operating coils HI and I13. The motorstarts to operate causing the planer platen to move in the cutdirection. The circuit for armature I3 extends from the energizedconductor 91, contacts I61, series field winding I5, conductor I15,contacts I59, conductor 11, armature I3, starting resistor I19, contactsI6I, conductor I09 to the energized conductor 81. The circuit foroperating coil I1I continues from conductor I11, through the operatingcoil I 1|, contacts I-8I.

conductor I89 to the energized conductor 81. 'Ihe circuit for theoperating coil I13 continues from conductor I11, operating coil I13,conductor I88, to the energized conductor 81.

Energization of operating coil I13 actuates field relay 39 to opencontacts I88 and close contacts III to preset the rheostat II3 so thatthe motor II may operate at a predetermined peed in the cut directionafter the circuit through contacts III has been opened.

Energization of operating coil I1I actuates plugging relay to closecontacts I83. Closure of contacts I 83 and I83 establishes a holdingcircuit for operating coil II to be utilized during certain operationsrequiring dynamic braking.

Opening of contacts I51 prevents energization of operating coil I85 whenthe attendant releases the depressed pushbutton 55.

Closure of contacts I89 establishes a circuit across the armature I3 foroperating coll I81. When the counter-electromotive oi the armature I3reaches a predetermined value, the operating coil I81 becomessufiiciently energized to actuate auxiliary relay 41 and close contactsI89. A circuit is then completed through operating coil I93 and itextends from conductor I29 through contacts I31, contacts I89, operatingcoil I 93 to the energized conductor 81. Energization oi. operating coilI93 actuate: starting switch 31 thus opening contacts I91 and closingcontacts I95.

Opening of contacts I 91 causes the deenergization of operating coil 93and thus the opening of contacts III to establish the circuit throughthe field rheostat 3 as hereinabove explained. Closure of contacts I95establishes a shunt circuit across the starting resistor I19. The motorthen continues to accelerate to its maximum predetermined speed in thecut direction.

As the planer platen proceeds in the cut direction and approaches thelimit of travel for which the dog 89 has been set, projecting lever 83is tripped, thereby opening directional contacts 13 and closingauxiliary contacts 15. Immediately thereafter the dog 89 actuates lever85, momentarily opening the circuit through contacts 8|. However, thecircuit for energizing operating coil 95 of auxiliary relay 43, ismaintained by the closure of auxiliary contacts 15.

The opening of directional contacts 13 opens the circuit throughoperating coils I33 and I3I. Deenergization of operating coils I33actuates dynamic braking switch 33 to close contacts I53 thusestablishing a dynamic braking circuit across the armature I3 of motorII. Deenergization of operating coil I3I actuates contactor 25 to opencontacts I81 and I89, and to close contacts I85.

Opening of contacts I81 disconnects the armature I3, and series fieldwinding I5 of motor II, and operating coils HI and I 13 from theenergized conductor 85. Opening of contacts I89 causes thedeenergization of operating coil I81 thus causing the opening ofcontacts I89 and thus the deenergization of operating coil I93 to opencontacts I95 and close contacts I 01. Closure of contacts I91 causes theactuation of field relay 31 to close contacts III thus increasing thecurrent through the shunt field winding I1.

After the actuation of directional contacts 13, the operating coil I5Iis maintained in the energized condition by a holding circuit whichextends from the upper side of armature I3 through conductor I11,contacts I59, conductor I15, contacts I85, contact-s I83, contacts I83,contacts I49, operating coil I5I, conductor 81, conductor I 89, contactsI8I, resistor I19 to the lower side oil I3. when thepotentiai acrossarmature I3 decreases to a predetermined value, the operating coil IIIof plugging relay actuates contacts I83 to open the above describedcircuit for operating coil III.

Deenergization of operating coil I-5I actuata reversing switch 21 toopen contacts I59, I81 and I83, and to close contacts III and I51.Closure of contacts I51 completes the circuit for operating coils I3I,I33 and I85 01 the main contactor 25, dynamic braking switch 33, andreversing switch 28, respectively. This establishes'the circuit forplugging and reversing the direction of rotation oi the motor I3 thuscausing the planer platen .to stop and then move to the left (Fig. 2),or in the return direction. As the planer platen I9 proceeds to theleft, dog 89 actuates lever 85 to momentarily open contacts 8|. throughthe operating coil 95 is maintained by the auxiliary contacts 15. Aninstant later, the dog 89 actuates lever 83 to close directionalcontacts 13 and open auxiliary contacts 15.

The operating coil I13 oi! field relay 39 is shunted by contacts I91 andtherefore maintained in the deenergized condition, thus presettingrheostat 3 so that motor I3 may accelerate to a predetermined speed inthe reverse direction. The operation of the motor and planer in .thereturn direction is substantially similar to that described for the outdirection; therefore, it is believed unnecessary to the undenstanding ofthe invention, to describe this operation. However, it will be notedthat as the platen approaches the'limit of travel in the returndirection, the dog 1I first actuates lever 81 to open directionalcontacts 11 and close auxiliary contacts 19. Immediately thereafter thedog 1I actuates the lever 85 to momentarily open contacts 8|. Itauxiliary contacts 19 are closed when contacts 8I are opened, thecontrol system continues to operate in the normal manner as hereinaboveexplained.

If, during operation in the cut direction, the directional contacts 13and the auxiliary contacts 15 tail to operate when the dog 89 wouldnormally actuate the projecting lever 83 as hereinabove explained, themotor M will continue to rotate at the normal operating speed.Immediately after the dog 89 passes projecting lever 83, it actuateslever 85 to open contacts 8|. Because the auxiliary contacts 15 and 19and the contacts I8I are in the open circuit position, the

As hereinabove explained, the-circuit momentary opening of cont-acts 8|deenergizes the operating coil 95 thus actuating auxiliary relay 43 toopen contacts I 25 and close contacts I23. Opening oi. contacts I25maintains the operatingcoil 95 in the deenergized condition and causesthe armature I3, series field l5, shunt field I1, and all of theoperating coils with the exception of operating coil 93 to becomedisconnected from the energized conductor 85. However, the shunt fieldwinding l1 ismaintained in the energized condition by the closure ofcontacts I23.v

The operating coil I5I is also maintained in the energized condition bythe holding circuit hereinabove described except that it will be notedthat contacts I 43 are now in the closed position, shunting contacts I83because operating coil I35 was deenergized by the opening of contactsI25. The closing 01 contacts I43 renders the contacts I83 ineffective,at this time, therefore, the operating coil I5I is maintained in theenergized condition alter the plugging relay H is actuated.

Deenergimtion of the operating 0011 I actuatm the dynamic braking switch33 to establish the dynamic braking circuit for armature I3 through thecontacts I95 and resistor I55.

Upon failure of directional contacts 13 to function, .the dynamicbraking effect is initiated an instant later than it would have been hadthe directional contacts I3 functioned. To stop the pl-alten I9 withinthe limit of travel predetermined by the actuation of projection lever63 by the dog 69, a relatively stronger dynamic braking effect isnecessary. This is accomplished by closure of contacts II I to shunt thefield rheostat II! and the resistor I 2|, thus overexciting the shuntfield winding I! at the beginning of the dynamic braking period. Thecircuit for the shunt field winding I'I now extends from the upper sideof armature I3 through conductor "1, contacts I59, conductor I15,contacts I23, conductor 9, contacts I, shunt field winding I1, conductorI09, contacts IG-I, starting resistor I19 to the lower side of armatureI3.

Once the dynamic braking effect has been initiated by the opening ofcontacts 8|, the motor speed rapidly decreases until both the motor I3and the platen I9 come to rest. As the motor speed decreases, thepotential across the armature I3 decreases, and when it reaches apredetermined value, the operating coil I5I becomes deenergized, thusopening contacts I59, I6-I and I53 and closing contacts II and I51.

Closure of contacts IIII establishes a circuit for reenergizingoperating coils 9I and 95 and shunt field winding I! as hereinabovedescribed with reference to the closing of the switch 99. When the causeof the failure of the limit switch SI has been corrected, the motor mayagain be started by depressing the appropriate pushbutton.

It will be readily understood that upon failure of the directionalswitch 11 and the auxiliary switch I9 to operate when the lever 61 isactuated by dog II when the platen I9 is moving in the return direction,the motor II will be stopped in a manner similar to that hereinabovedescribed.

I do not wish to be restricted to the specific structural details,arrangement of parts or circuit connections herein set forth, as variousmodifications thereof may be efiected without departing from the spiritand scope of my invention. I desire, therefore, that only suchlimitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In a control system, in combination, means for stopping a motoroperating at a given speed in a predetermined interval of time, meansresponsive to the operation of the motor for stopping the "motor priorto the end of said predetermined interval of time in event of a failureof the first named means.

2. In a control system, in combination, means for stopping a motor,operating at a given speed, in a predetermined interval of time, meansactuated in response to the operation of the motor subsequent to thefirst named means for stopping the motor substantially at the end ofsaid predetermined interval of time in event of a failure of the firstnamed means.

3. In a control system, in combination, means for stopping a motor froma given speed in a predetermined interval of time and means operable inresponse to the motor operation after a failure of the operation of thefirst named means adapted to stop the motor within the predeterminedinterval of time.

4. The method of stopping an electric motor I connecting the motor fromthe source of power,-

and initiating a dynamic-braking eil'ect that will stop the motor withinthe limit of travel predetermined by the directional limit switch.

5. The method of stopping an electric motor connected to a source ofpower and coupled for driving a reciprocating member by utilizingemergency stoppin means upon failure of the member to actuate adirectional limit switch normally adapted to initiate means for stoppingand reversing the motor when the member reaches a predetermined limit oftravel, which comprises, actuating. emergency stopping means subsequentto the normal operating time of the directional limit switch,disconnecting the motor from the source of power, and initiating a.dynamic-braking effect on the motor that will stop the member within thelimit of travel normally predetermined by the directional limit switch.

6. Tne method of stopping an electric motor connected to a source ofpower and coupled for driving a reciprocating member, having emergencystopping means associated therewith upon failure of the member toactuate a directional limit switch normally adapted to initiate apredetermined dynamic-braking efiect for stopping the motor when themember reaches a predetermined limit of travel, which comprises,actuating emergency stopping means subsequent to the normal operatingtime of the directional limit switch, disconnecting the motor from thesource of power, and initiating a dynamic-braking eifect, stronger thanthe dynamic braking effect normally initiated by the directional limitswitch, on the motor for stopping the member within the limit of travelnormally predetermined by the directional limit switch.

7. In a control system for a. reciprocating member operated by areversing motor, a source of power for the motor, control meansinitiated by the reciprocating member for effecting the reversal of themotor when the said member has reached a predetermined limit of travel,and stopping means, cooperatively associated with the said controlmeans, operated by the said member for stopping the motor before thesaid member reaches the predetermined limit of travel upon failure ofthe control means to function in a predetermined manner.

8. In a control system, in combination, a reciprocating member, a motorfor driving the member, a source of power for the motor, a main lineswitch for connecting the motor to the source of power, reversingswitches for the motor, directional switches operated by the member forselectively effecting the reversal of the motor, and a limit switchcooperatively associated with the directional switches and operated bythe member for stopping the motor upon failure of the directionalswitches to function in a predetermined manner.

9. In a control system for a machine element, in combination, means formoving the element, stopping means for said element set in operation bysaid element when in a given position and adapted to stop the element ina given distance of travel beyond said given position, and means,actuated by the said element and operable in the event of failure of thestopp g means, adapted to stop the element in substantially the samedistance of travel of the element beyond the said given position. l

10. In a system of control for an electric inotor having a rotor, incombination, means for energizing the motor to cause the rotor tooperate at a substantially constant speed, normal stop ping means forthe rotor set in operation when the rotor in its rotation holds a givenposition in space and adapted to stop the rotation of the rotor in agiven number of revolutions after the rotor holds said given position inspace, and emergency stopping means, responsive to the operation of themotor, operable upon failure of the normal stopping means and thus setin operation later, namely, when the rotor in its rotation has movedbeyond said given position, adapted to stop the rotor in a number ofrevolutions that is equal to or less than the diiference between thesaid given number of stopping revolutions of the rotor when stopped bythe normal stopping means and the number of revolutions the rotor hasmade between the time the rotor holds its given position in space andthe time the stopping eifect of the emergency stopping means isinitiated.

11. In a system of control for a machine element, in combination, meansfor moving the machine element in a given direction toward a limitingposition beyond which the machine element is not to move, normalstopping means, set in operation by the machine element when a givendistance from the limiting position, adapted to retard the machineelement at a given average rate to effect a complete stopping of themachine element at the limiting position, and emergency stopping means,set in operation by the machine element a lesser distance from thelimiting position in. the event of failure of the normal stopping means,adapted to retard the machine element at a higher average rate to effecta com- 5 plete stopping of the machine element before movement to thelimiting position.

12. The method of stopping an electric motor connected to a source ofpower upon failure of the motor to actuate control means normallyadapted to stop the motor at a predetermined limit of travel, whichcomprises, disconnecting the motor from the source of power, andinitiating a dynamic-braking effect that will stop the motor within thelimit of travel predetermined by the control means.

13. In a control system, in combination, means for stopping a motor froma given speed in a predetermined interval of time, an auxiliary switchmechanically coupled to said stopping means, additional stopping meanselectrically connected to said auxiliary switch and responsive to theoperation of the motor for stopping the motor prior to the end of saidpredetermined interval of time in the event of a failure of the firstnamed means.

14. In a system of control, in combination, stopping means for stoppinga motor, operating at agiven speed, in a predetermined interval of timeafter initiation of the stopping operation of the motor by said stoppingmeans, and second stopping means, responsive to the operation of themotor, and set in operation prior to the end of said predeterminedinterval of time for stopping the motor prior to the end of saidpredetermined interval of time in the event of a failure of the firstnamed stopping means.

' GEORGE E. KING.

